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September 9, 2004 Electrical Safety Division Mission To provide miners with a safe work environment, by ensuring equipment is safely designed for its intended use and to implement new technologies to address existing and emerging concerns.

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September 9, 2004 Product Evaluation Intrinsically safe circuits shall be incapable of releasing enough electrical or thermal energy to cause an ignition in a methane and air mixture. The surface temperature of enclosures and components of intrinsically safe circuits that could be exposed to coal dust shall not cause thermal ignition of a coal dust layer.

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September 9, 2004 Product Evaluation All circuits are evaluated under the following conditions: One independent fault Normal operation Two independent faults A Safety Factor on Energy is also applied

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September 9, 2004 Processing Time MSHA approval time could decrease, if… –Results of Testing and Evaluation performed by an Independent Laboratory are accepted by MSHA MSHA approval time could increase, if… –Insufficient evaluation resulting in repeat or additional testing –Incorrect testing, repeat test (s) necessary

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September 9, 2004 Approval Numbers If an independent laboratory performs one, some, or all of the evaluation or testing, the approval number will still have the MSHA approval number. The final rule does not require that manufacturers use the mark of the independent laboratory that tested and evaluated the product or its components. However, nothing in this final rule prohibits a manufacturer from using the mark of an independent laboratory if it chooses to do so, as long as it carries the MSHA mark as well.